In a radio frequency signal transmission system, there is a need for providing signal sources with a great variety of signal types and adjustable parameters to investigate the behavior of an RF device under test, short: DUT. To provide such signal sources, signal generators are used. RF signal generators are used for testing components, receivers and test systems in a wide variety of applications including cellular communications, WiFi, WiMAX, GPS, audio and video broadcasting, satellite communications, radar and electronic warfare. RF and microwave signal generators normally have similar features and capabilities, but are differentiated by frequency range. RF signal generators typically range from a few Kilohertz to some Gigahertz, while microwave signal generators cover a much wider frequency range, from less than 1 Megahertz to at least tens of Gigahertz. Some modules go up to about hundred Gigahertz when used with external waveguide source modules. RF and microwave signal generators can be classified further as scalar or vector signal generators. In the following, the term RF signal covers both radio frequency signals and microwave signals.
In order to be suitable for the maximum possible number of such investigating- or measuring-applications of a DUT, the signal generator must provide an extremely wideband radio frequency range with very high frequency resolution.
To properly investigate the behavior of a DUT, RF signals with an adjustable attenuation or amplification signal amplitude need to be generated.
An RF attenuator is an electronic device that reduces the power of a signal without appreciably distorting its waveform.
An attenuator is effectively the opposite of an amplifier, though the two work by different methods. While an amplifier provides gain, an attenuator provides loss, or gain less than 1. Hereinafter, the term “attenuator” does not exclude an amplifying function of an attenuator.
Currently-available signal generators are specified to provided either RF signals or microwave signals depending on their frequency range.
In document US 2008/0258833 A1, a signal generator is described that comprises a common level adjustment device for a low frequency range signal path and a high frequency range signal path. Problematic with such a common level-adjustment device is the inability to operate radio frequencies of a wide range of frequencies, such as from DC to higher RF signals, such as tens of Gigahertz. Thus, either the lower frequency ranged signals or the higher frequency ranged signals are not attenuated properly.
Thus, there is a need for providing an RF attenuator which is useful in a wide range of applications and which can flexibly be used for different DUT testing scenarios. The RF attenuator should be useful to operate radio frequencies of a wide range of frequencies, such as from DC to higher RF signals, such as tens of Gigahertz. The attenuator should comprise an attenuation ramp of several decades of decibel.